Hall-effect current clamps are well known. Connected to a multimeter (millivoltmeter), to an oscilloscope or to a plotter, they permit measuring the strength of a direct or alternating current and/or visualizing the shape of the current. Such current clamps are marketed, for example, by the company Bell Inc., under the designation "Current Gun" Model CG 100 A, or by the Beckman Corporation under the designation "AC/DC Current Clamp" CT 233. These known clamps have a relatively high current consumption and, as a result, the batteries which are used to supply them with current have a relatively short life span. For instance, the Bell CG 100 A current clamp is supplied under 6 V (four 1.5 V Type AA batteries) and consumes about 40 mA, or a consumed power of 240 mW. The life span of the batteries is about 30 hours with alkaline batteries and about 60 hours with mercury batteries (data furnished by the manufacturer). The Beckman CT 233 current clamp is supplied under 9 V (one 9 V Type 6 LF 22 battery) and consumes about 15 mA (data furnished by the manufacturer), or a consumed power of about 135 mW. Inasmuch as the 9 v Type 6 LF 22 batteries have a capacity of about 500 mA.h the life span of the battery with the Beckman clamp is, therefore, about 30 hours.
Hence, the purpose of the present invention is to provide a current clamp having a current consumption noticeably less than that of the abovementioned known clamps and, consequently, permitting a greater autonomy of the batteries being used for its supply.